Light sensitive tube



I July 5, 1938. i5. GRLlcl-l LIGHT SENSITIVE TUBE Filed Aug. 6, 1936 mvENToR Daal @k/z'c- ATTORNEY.

`Patented July 5, 1938 UNITED STATES PATENT GFFICE l 2,122,860 LIGHT SENSITIVE TUBE Paul Grlich, Dresden, Germany, assignor to Zeiss Ikon Aktiengesellschaft, Dresden, Germany Application August s, 1936, serial No. 94,589

InG

ermany August 8, 1935- 2 claims. (ci. 25o-27.5)

photoelectric tube equipped with a thin light sensitive layer of this type is particularly suitable for television purposes, since this tube permits the construction of a television apparatus which is adapted for taking television images at day light.

rThe accompanying drawing illustrates diagrammatically a photoelectric tube provided with a p hotoelectrc cathode in accordance with the present invention.

. The envelope I of the tube contains an anode 2 and a photoelectric cathode 3. The latter may consist of a layer of antimony or bismuth and a layer of rubidium or caeslum alloyed together. In the present instance the photoelectrlc cathode 25 is` mounted on the lnnergwall of the envelope I. The method for producing the-light sensitive layer of the invention is asfollo'wsz A thin layer of antimony o r bismuth is precipitated by evaporation upon a suitable carrier. layer then preferably is treated with oxygen or its homosufficiently thin to remain pervious to light. A

violet portion of lthe spectrum.

logues, whereby the oxygen is adsorbed on the layer. Subsequent to this operation caeslum or rubidium is precipitated by evaporation upon the antimony or bismuth layer respectively prepared in the described manner. By a heattreatment of the layers, the caesium or rubidium respectively ls caused to enter into the antimony or bismuthlayer respectively and forms an alloy. The composite coating produced in this manner is extremely sensitive to light and possesses a sensitiveness covering-the entire visible range of the spectrum.

If the light sensitive layer is not required to be pervious to light, then the above elements may be precipitated to greater thickness. However, care must be taken always that the alloy will be produced. The employment'of rubidium in place of caeslum will produce a tube whose highest light sensitiveness is displaced more toward the ultra- 20 What I claim as my invention is:

1. A photoelectrlc cathode comprising a bismuth layer and a caeslum layer alloyed together. 

